Was there a large fluctuation in temperature that might account for the fall? That was a quick turn, for sure. I brewed an Octoberfest Sunday and it pretty much finished by this morning (Thursday). Temperature went up to 58F at high krausen and is now back to ambient (in a fridge) 52F. I pitched a slurry from a prior batch of Vienna after racking that beer (one week from brewing). I have no experience with K-97, however. Sounds like a beast.